In recent years, mobile stations represented by cellular phones have been spread, the market of the mobile communication systems have been expanded, and services of the mobile communication systems have been diversified. The 3rd Generation Partnership Project (3GPP) standardizes Long-Term Evolution (LTE) and LTE-Advanced, which is one of advanced wireless access technologies for the fourth-generation mobile communication technology, for the purpose of achieving high-speed large-capacity communication.
The LTE-Advanced includes a new function called Dual Connectivity (DC). The DC is a function for achieving large-capacity communication in which a Master evolved Node B (MeNB) is responsible for mobility and wireless resource management and a Secondary evolved Node B (SeNB) is responsible for only user data communication. However, the user data communication is possible in the MeNB as well.
To further increase the communication capacity, a locally operated base station, that is, a base station that covers a small area such as the SeNB is expected to use a high-frequency band. Implementation of a beam forming function is examined for the purpose of loss compensation because a radio wave propagation loss is larger in a higher frequency band. The beam forming function, which uses the beam having a high directivity, changes the direction of the beam where appropriate such that a mobile station that communicates with the base station obtains a high gain, thereby achieving the satisfactory communication. For example, Patent Literature 1 discloses a radio base station that changes, where appropriate, the parameters used for the beam forming and the like in accordance with the change in the surrounding environment.